In a wireless communications system using spread spectrum techniques, such as those operating in accordance with various CDMA or UMTS standards, the same wideband radio carrier is reused within every cell; i.e., all transmissions share the same radio spectrum. Accordingly, all mobile terminals (referred to as “mobiles” hereinafter) that are simultaneously transmitting interfere with one another. This co-channel interference is managed and controlled through a variety of strategies. The universal use of the same radio carrier within CDMA/UMTS systems means that the achievable air interface capacity is dictated by the amount of background co-channel interference that can be tolerated without a compromise in performance (e.g., such as a reduced voice quality) and by limits on transmitter power (e.g., the downlink transmitter in the transmitter must have sufficient power to enable a receiving mobile to overcome the background interference).
The tolerable background co-channel-interference varies considerably from cell site-to-cell site and even from sector-to-sector in a service provider's coverage area, rendering predictions of air interface capacity difficult. Before a network is put into service by a service provider, a direct pre-commercialization evaluation of capacity of that network is of great interest to the service provider in order to confirm that the capacity of the network as designed is actually sufficiently large enough to handle expected traffic levels. Such an evaluation of a cell site's traffic handling capacity can be performed by flooding the network with live users and observing the responsive performance of a one or more test mobiles in the network's coverage area. Such a procedure is logistically difficult at best. Although such a methodology allows direct measurement of capacity (i.e., the system is loaded until observed performance is compromised), in practice it is often proves infeasible since it requires orchestration of a large number of field mobiles and associated test personnel.
Accordingly, a methodology is highly desirable that permits an estimate of downlink capacity to be determined in a simpler and more accurate manner.